Given specific operational data about a gravity thickener, what should an operator do if the sludge pump rate is low and the sludge blanket depth is increasing?

• A. Decrease the pump operating time
• B. Increase the pump operating time
• C. Flush the system with fresh water
• D. Stop operations for cleaning

Answer: (B)

When a sludge pump operates at a low rate while the sludge blanket depth is increasing in a gravity thickener, it indicates that the solids are not being effectively removed from the tank. As the sludge blanket deepens, it can create operational issues, including reduced efficiency of the thickening process and potential overflow if the blanket becomes too deep.

Increasing the pump operating time can help to address this issue by enhancing the removal of excess sludge from the gravity thickener. By allowing the pump to operate longer, more sludge can be extracted, which helps maintain an optimal sludge blanket depth and ensures that the thickening process continues effectively. Proper removal of sludge prevents the thickener from reaching a point where overloading could lead to system inefficiencies or failures.

This approach strategically adjusts the throughput of solids from the thickening process, aiming to restore balance and operational effectiveness.